Exemplary conventional honeycomb structure extrusion dies and methods of making same are disclosed in U.S. Patents to Harkenrider U.S. Pat. Nos. 3,038,201 and 3,038,202, to Bagley U.S. Pat. Nos. 3,790,654 and 3,905,743 and to Benbow et al U.S. Pat. No. 3,824,196. In Harkenrider, a die body is provided with a large number of feed passages which are axially drilled from one end surface towards the other end surface separately, interconnected extrusion slots which are formed from the other end surface of the die body and have the same shape and size as those of the cross sectional shape of walls of an obtained honeycomb structure, and round pooling holes which are radially drilled in such positions as to connect the feed passages with the interconnected extrusion slots.
In the conventional extrusion die having the above described structure, an extrudable material which is supplied through the feed passages is temporally pooled in the round pooling holes and then the material is fed into the interconnected extrusion slots.
The extrusion die provided with the above described round pooling holes is generally made as follows:
Namely, a die body having the desired shape and size is prepared from a metallic block. Feed passages in large number are drilled in the die body from one end surface towards the other end surface in an axial direction. Interconnected round extrusion holes are formed from the other end surface towards one end surface. Round pooling holes are radially drilled from one side surface of the die body to the side surface opposed thereto so as to connect the feed passages and interconnected extrusion holes. All of the above passages and holes are formed in one single unitary metallic die body.